Re: [PATCH] vmscan: improve reclaim throuput to bail out patch

I evaluate rvr bailout and skip-freeing patch in this week conteniously.
I'd like to dump first output here.



Rik, could you please review following?
==
vmscan bail out patch move nr_reclaimed variable to struct scan_control.
Unfortunately, indirect access can easily happen cache miss.
More unfortunately, Some architecture (e.g. ia64) don't access global
variable so fast.

That is amazing. Especially considering that the scan_control
is a local variable on the stack.

Ahhhhh, I did want to write "indirect access(or likes global variables)",
but my brain was sucked. sorry.

I'll post description fixed version soon. thanks.


if heavy memory pressure happend, that's ok.
cache miss already plenty. it is not observable.

but, if memory pressure is lite, performance degression is obserbable.

about 4-5% degression.

Then, this patch introduce temporal local variable.

OK. the degression is disappeared.

I can't argue with the numbers, though :)

Maybe all the scanning we do ends up evicting the cache lines
with the scan_control struct in it from the fast part of the
CPU cache?

Yeah, I think so.



Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>

Acked-by: Rik van Riel <riel@xxxxxxxxxx>
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